1. Technical Field of the Invention
The present invention relates to novel dispersing agents for solid plant-protection formulations, for the preparation of dispersible plant-protection granules and to said granules themselves.
2. Description of the Prior Art
Solid plant-protection formulations, namely, "wettable powders" and "dispersible granules," are agrochemicals currently being widely developed because they avoid the use of potentially toxic solvents and may be sealed in packaging which is conveniently recyclable, or in water-soluble sachets. The applicator or user thereof is thus better protected.
Other than the plant-protection active agent, these solid formulations include dispersing agents, binders and wetting and disintegrating agents. Such formulations are typically prepared by pregrinding the solid active agent(s) with the various solid additives, and then converting same, by adding water thereto, into a concentrated dispersion which is subsequently agglomerated in a pan agglomerator or in a turbosphere, or which is extruded prior to being dried via fluidized bed technique, or which can be spray-dried.
To date, the dispersing agents employed therefor must be solid; these are characteristically polymers such as lignosulfonates (sodium, calcium or ammonium salts), maleic anhydride/isobutylene copolymers (sodium or ammonium salts), condensed phenylsulfonic acids (sodium salts) or condensed naphthalenesulfonate/formaldehyde polymers (sodium or ammonium salts).
The aforesaid restriction is due to the requirements of the processing, which does not permit the addition of a liquid additive, unless a premix in water is desired which will subsequently be employed for the granulation.
Consequently, surface-active agents (surfactants) which are liquid or viscous at ambient temperature, such as ethoxylated alkylphenols or ethoxylated di- or tristyrylphenols, conventionally employed as dispersing agents in liquid formulations (in particular in microemulsions, concentrated emulsions, emulsifiable concentrates or concentrated suspensions), in this instance cannot be used. Furthermore, when these materials are evaluated in solid formulations, in particular in "dispersible granules," it is found that, besides the fact that they are difficult to process, they are not good dispersants, i.e., they produce granules which have a mediocre dispersibility and suspensivity.